Built for situations where standard markers just aren't enough, Avery® Marks A Lot® UltraDuty™ markers are ideal for construction sites, warehouses, workshops and more. Avery® industrial markers work great on plastic, wood, metal and concrete. The durable tip also works on abrasive, dusty, wet and oily surfaces without clogging. Specially engineered to resist water, abrasion and smearing, the heavy-duty ink makes sure that writing lasts through the harshest conditions. The cap also features a clip to keep markers secure in pockets and to prevent rolling off of surfaces. Marker Ink Type: Permanent; Marker Tip Type: Chisel; Marker Tip Size (text): Medium; Marker Tip Size (numeric) 5 mm.